1. Field of the Invention
The present invention relates to a method and apparatus for delivering a medical device into a body cavity.
2. Description of the Related Art
Delivery of drugs to organs such as the bladder are typically accomplished systemically. Systemic drug delivery through oral, intravenous, intramuscular or transdermal administration methods carries with it the obvious drawbacks of any systemic treatment, such as side effects. The drug may also be metabolized or altered by physiological processes and the ultimate quantity of active drug that reaches the organ may be reduced. In addition, because many drugs are not well tolerated systemically, the dosage must be limited, thereby reducing the total effective dose that reaches the organ.
Delivery of drugs to organs such as the bladder can also be accomplished by retrograde injection of the drug into the bladder, by a catheter. Retrograde introduction of a drug by a urethral catheter, however, is suitable only for limited situations and has inherent drawbacks.
See for example, Bladder Tissue Pharmacokinetics of Intravesical Taxol, Song, D, Wientjes, M G, Au, J L, Cancer Chemotherapy and Pharmacology, 1997, 40(4): 285-92; The Pharmacokinetics of Intravesical and Oral Oxybutynin Chloride, Massad, C A, Kogan, B A, Trigo-Rocha, F E, Journal of Urology, 1992, August, 148(2 Pt 2): 595-7; Advances in Drug Delivery and Targeting, Goldstein, D, Lewis, C, Current Opinion in Oncology, 1991 Dececember 3(6): 1096-104; and Intravesical Hyaluronic Acid in the Treatment of Refractory Interstitial Cystitis, Morales, A, Emerson, L, Nickel, J C, Urology 49 (Suppl 5A): 111-113, 1997. Retrograde introduction of drug via urethral catheter is primarily used only in a hospital or managed care situation. It is not suitable for treatment of chronic urinary-tract conditions.
Stephen et al., U.S. Pat. No. 5,301,688, discloses a method for treating bladder cancers through electromotive administration of drugs into the bladder via a catheter. This type of treatment is suitable primarily for care administered on an in-patient or out-patient basis, not for chronic treatment.
Tsukada, U.S. Pat. No. 5,219,334 discloses an infuser for connection to a catheter that is suitable for long-term delivery of drug into a patient through the catheter. This device requires continuous catheterization in order to function adequately.
Pryor et al., U.S. Pat. No. 5,062,829, discloses a helical device for insertion into a body cavity, e.g., the rumen of a bovine. The helical device includes a drug that can be released over time and further includes a biodegradable portion so that, upon exhaustion of the drug, the device can break up and be naturally eliminated.
Garay et al., U.S. Pat. No. 4,925,446, discloses an infusion device having an annular shape that is suitable for delivering materials into the stomach over a prolonged period of time.
None of these prior art devices address the problem of intravesical drug delivery where drug delivery is intended to continue over a prolonged period of time while the patient maintains an active lifestyle.
Two of the major causes of urge incontinence are detrusor instability and hyperreflexia. Oxybutynin is a pharmacological agent that has been used to treat urge incontinence with some success. This drug is an anticholinergic agent that blocks contraction to the bladder and has direct smooth muscle relaxant properties. Unfortunately, this drug is associated with significant side effects upon oral administration, including dry skin, dry mouth, blurred vision, constipation, and urinary retention. In patients with cardiovascular disease, oxybutynin may lead to tachycardia. Because of the side effects, the accepted oral dose of oxybutynin is limited to 10-15 mg per day.
Interstitial cystitis is a debilitating condition in which the lining of the bladder is irritated, creating a sense of urgency and pain. The condition results in extreme frequency of urination, sometimes as many as 40, 50, or more times per day and can lead to cystectomy. Sufferers of interstitial cystitis can be treated by administration of certain drugs, including pentosanpolysulfate, manufactured by Bene of Munich, Germany and distributed by ALZA Corporation of Palo Alto, Calif. under the trademark ELMIRON. However, there is currently no satisfactory method for delivery of pentosanpolysulfate to a patient over a prolonged period of time while permitting the patient to enjoy a relatively normal lifestyle.